Digital Video Data Rate

First of all, I’d like to thank Lynne D. Johnson for the opportunity to blog as a Fast Company Expert.

There are many reasons a particular digital video might not run well, or at all, on your computer. You might not have enough processor speed. Your video card might not be able to handle the task. You may not have the necessary codec installed. If you can see and hear the video, but it doesn’t run smoothly, your best bet is to lower the data rate. It might seem that the answer lies in decreasing the frame size. A smaller video should run more smoothly than a larger video, right?

In most cases, digital video being presented on a computer or over the internet has been compressed. By definition, the video you are watching is “smaller” than the original video. It’s smaller in size (perhaps 320×240 when the original was 640×480), but it’s also smaller in file size, or the amount of space it takes up on your drive. The parameter that limits your frame size is independent of the parameter that limits your data rate. If you decrease the frame size without decreasing the data rate, you end up with a video with a smaller viewing size that takes up the exact same amount of space on your drive.

Data rate is measured in kbps (kilobits per second or thousands of bits per second). You can set a data rate limit when you compress a digital video. If you leave the frame size the same as the problematic compression attempt and decrease the data rate, you end up with a smaller file size as well as a video that demands less processing power.

Eventually, you’ll get the video down to a manageable data rate for your computer. Hopefully, the video still looks good. If it doesn’t (since there’s now much less data per second making up each frame), you have the choices of either decreasing your frame size or decreasing your frame rate to get the visual quality where you want it now that you’ve dealt with your performance issues.

Bill Cammack • New York City • Freelance Video Editor •

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